1. Field of the Invention
This invention relates to a recording apparatus capable of varying the length of identification (ID) data of recording data in a bit unit and/or improving reliability of data transfer between a host computer and a recording medium by use of an error detection/error correction function.
2. Description of the Related Art
Technique relating to conventional recording apparatuses such as a magnetic disk control apparatus is described, for example, in the instruction manual of "HD64950S" (a hard disk controller of Hitachi, Ltd.). Thereby, identification (ID) data is generated at the time of disk formatting and contains cylinder address data, head address data, sector address data and flag data. The length of each data is set and fixed in a byte unit. At the time of search for a sector, ID data of an object sector and read ID data are compared with each other, and whether or not the sector corresponding to the read ID data is the object sector is judged on the basis of coincidence or non-coincidence of the ID data as a whole.
However, the prior art technique described above does not much take into consideration the reduction of a storage region for storing the ID data which reduction is required with a greater capacity and higher performance of a magnetic disk apparatus, or in other words, optimization in accordance with a necessary data quantity, and diversification of ID data searching functions.
The conventional recording apparatus is equipped with a error detecting and error correcting function for data transfer between a recording medium and a data buffer but does not have such a function for data transfer between a host computer and the data buffer. For this reason, even when erroneous data is transferred from the host computer to the data buffer, the error cannot be detected and corrected, so that reliability of the entire system inclusive of the disk apparatus tends to remarkably drop.
Furthermore, a check symbol added to data to be recorded is only one kind. Therefore, when any-error occurs in the check symbol itself or when the check symbol becomes non-reproducible, the data is likely to be judged as wrong or the error correction cannot be made correctly even though the data itself does not contain any error.
Data is recorded dividedly in each sector as a recording unit, and reproduction of the data is made in this sector unit. In this case, no problem occurs if the data of only one sector is reproduced but when a plurality of sectors are reproduced continuously, the following problem occurs. The data reproduced from a recording medium become sequentially the object of error detection processing in an error detection/correction circuit (ECC) and the error correction processing is executed if any error exists. When the error is detected in the data reproduced from any of the sectors other than the last sector, the data from a next sector is reproduced while the error correcting processing is being made for this sector data, so that the error detection processing cannot be made for the next sector data. For this reason, conventionally, after one rotation of the disk is waited for, the next sector data is reproduced and is subjected to the error detection processing. According to this method, however, the data read-out operation is retarded by the time corresponding to one rotation of the disk, so that data transfer performance is deteriorated drastically.